Continuous conveyer furnace



Nov. 15, 1932. B. M JOHNSON- 1,887,904

CONTINUOUS CONVEYER FURNACE Filed May 22. 1929 3 Sheets-Sheet 1 l F'z' 1. 1

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i '/z I, r o o ,5 WARE I I l l I l O O INVENTOR BOYD M. JOHNSON ATTORNEYS Nov. 15, 1932. I JOHNSON 1,887,904

commuous CONVEYER FURNACE Filed ma zz. 1929 a Sheets-Sheet 2 INVENTOR BOYD M. JoHNsoN ATTORNEY I UNITED STATES rATENroFFicE Patented Nov. 15, 1932 BOYD 1a.} JOHNSON,

COMPANY, or NIAGARA FAL S, NEW YORK, A CORPORATION or PENNSYLVANIA CONTINUOUS ooNvitYnR' romance Application filed May 22,

My invention relates particularly to improvements in continuous conveyer furnaces and drlers where it is deslred to transport articles continuously at a slow rate through long drying and heating chambers. It has been found in using such furnaces that so much heat may be lost by radiation, convection and conduction through the ends of the furnaces that the desired temperature cannot be maintained at the center. The temperature that can be maintained in the central portion of the heating furnace where the ware is fired has been found to be also much influenced by the number and size of articles that are being treated. a

I have found means to cut down effectively the losses referred to above. These means are illustrated by the accompanying drawings, which are more or less schematic, and in which: V a

Figure 1 is an elevation giving an end viewof a furnace having adjustable doors through whicha basket laden with ware is passing;

Figure 2 is a diagrammatic plan View showing the generalarrangement of a continuous conveyer furnace embodying my invention;

Figure 3 is an elevation showing a removable shield; V Figure 4 is an end elevation of a tunnel'kiln or furnace, showinganother shield arrangement and its relation to the tunnel, there being three shields one of which is. removable and the others fixed;

Figure 5 is a view generally similar-t0 Fig. 4 in which all theshields are removable;

Figure 6 is a view similar to Fig. .4 in which the ware under treatment is indicated by dotted lines; I y

Figure 7 is a diagrammatic plan'view'of a mod fied continuous conveyer furnace in which the radiation lo ses from the combus= tion chamber are reduced turning the'ends of the kiln at right angles to the central portion; I 1

Figure 8 is a diagrammatic plan view of another modification chamber is indicated as connected with a continuous conveyer furnace having its ends bent in opposite directions;

in which a drying 1929. Serial No. 365,206.; I

Figure 9 represents a modificationof the type indicated in Fig. 8 in which. the drying chamber and combustion. chamber are separated;

Figure "10 plan View of a combined continuous conveyer furnace and drier in which the ware iscarriedithrough the furnace in a prolonged tortuous path; I

Figure ll'is a vertical section of a further modification in which the furnace and dry; ing chamber are in vertically disposed relation;and"

Figure 12 is a verticalsection on the line 1212offFig. '11 in which the hangers and loads are indicated diagrammatically.

or METUCHEN; NEW JERSEY, ASSIGNOR 'r o THno-ARBGRUNDUM Referring to the drawings in more detail. 2

is a combustion'chamber through which the ware passes in the direction of the arrow A after being preheated in the chamber 3, which the wareenters usuallyafter a preliminary dryingin chambers such as are indicated in Figures Sand 9 at 22 and 22 respectively. Opposite the preheating chamber is an exit or cooling chamberB. The waste gases move as indicated by the-arrow B in a directionopposite to that of the ware. The ware is carried through'the tunnel kiln by means of a conveyer 4. from which is suspended a basket 5 by means of a hanger 6. The hanger 6 passesthrough a slot 7 in the roof of the furnace. The hanger 6 carries a sealing plate 9 which rides on' pipes 10 which may be watercooled. A guide member 13 may be used to aid in keeping the hanger 6 in the middle of theslot.

- The shields 8 play an important part in the economy of the furnace operations since they reflect a portion of the radiation toward the hotter part of the furnace. They tend to prevent loss of the heat by convection as well as" by radiation. The size of the openings through which the travelling shields and.

warepass may be adjusted by means of the adjustable doors 11. These shields may be attached or removed readily by having the shields slotted as indicated in-F-igure 3. r The shields may be made up. in parts as shown-in Figure 4 where'8" is a portion of a shield permanently attached to the basket and 8! is is still another diagrammaticf Shields may be carried on the baskets in this a removable portion of the shield. In this case the ware 12 itself acts as a radiation shield for a portion of the cross-sectional area As shown in Fig. 2, the shields are prefer ably so positioned thatthere is at all times at least one shield in the preheating chamber 3 and in the exit chamber 3. This assures of there being no direct open channel along the path of travel of the ware from either end of the firing chamber directly to the atmosphere. Another method of cutting down lossby radiation isillustrated in Figures 7, 8, 9 and 10. As shown in Figure 7 the end 23 of the preliminary heating chamber and the end '24 of the cooling chamber are shown as turned at right angles to the combustion chamber 2'.

This arrangement gives a continuous conveyer furnace in which the interior conditions more closely resemble those of a black body than is the case in a straight tunnel :kiln. The expression black body is used here in the sense employed in treatises on radiation. Briefly, a black-body is one whose emissivity is 100 percent. This condition is reached practically in the case ofa nearly enclosed muffle in which the temperatureof the inner lining is measured through an opening which is small as compared with the total area of the incandescent lining. In Figure 8 a continuous conveyer furnace is shown in which the ends 23 and 2% are turned at right angles to the combustion chamber 2" and in opposite directions. In this case the preliminary heating section of the furnace is continuous with the drying chamber 22. In Figure 9 the ends 23" and 24C" of the continuous conveyer furnace are shown as turned in the same direction at right angles tothe combustion chamher. The drying chamber is in this case not continuous with the furnace. In Figure 10 the drying chamber 22".issufliciently ex-.

tended in two horizontal dimensions so that the ware can be carried in a long tortuous path through the drying chamber.

In Figures 11 and 12 the drying and heating chambers are vertically disposed with respect to each other and the slot is formed in an intermediate partition separating the heating chamber and drying chamber. The conveyers in this case comprise an endless chain 1a to which is welded or otherwise secureda plurality of shafts 15 on which the wheels 16 are free toturn. The baskets 5 are also loosely mounted on the shafts 15. The chain 14 is driven continuously by the sprocket wheel 17. The latter is driven by a shaft 19, which is turned by outside means connected to a gear 20 keyed on the shaft 19.

the losses by radiation and convection in a stralght conveyer fLlI'llELCQ'WllJh slotted roof are ordinarily so great as to prevent the proper heating of the ware. As compared with furnaces having stationary charges large amounts of heat are carried away by the ware. There are ordinarily extensive radiation losses from the main heating chamber to the extended sections which are used for preheating the ware before the firing operation and for cooling it after the firing operation. There are also ordinarily serious convection losses through the slotted roof and through the end doors. I reduce the losses through the slotted roof by means of seals asindicated in Figure 1. The convection losses through the end doors are reduced by the plurality of shields used in connection with end doors of adjustable size.

The bending of the ends of the continuous conveyer furnace, as indicated in Figures 7, 8, 9 and 10 at both ends and at one end in the modification'shown in Figuresv 11 and112, contributes to compactness of design. Moreover loss by radiation and by convection is reduced. The radiation from the firing chamher is subjected in the extensions to a series of multiple reflections whichgives conditions more resembling that of anenclosed mufile than is possible with the ordinary straight continuous conveyer furnace. 7 f

- While the ends ofthe furnace are shown as bent at right angles to the main body of the furnace, I do not desire to limit myself to thisparticular angle or to the particular L-shaped extensions shown in the drawings. Either one or both ends of the furnace may be bent. Furnaces of this kind are adapted for the firing of enameled ware and the burning or heat treating of various ceramic or other articles.

The general object of my invention is to produce a greater uniformity'of temperature in continuous conveyer furnaces where articles are transported continuously or intermittently for successive heat treatments.

I claim:

1. A continuous furnace into which articles to be fired are continuously fed and. from which articles which have been fired are continuously discharged, having an endless conveyer therealong for transporting successive articles to beheat treated therethrough, and shields supported by the conveyer traveling with the ware and arranged transversely to the direction of travel of the ware, to retard the transmission of radiation through the series of spaced transverse vertical shields and horizontal shields closing the slotted roof attached to said supporting means to reduce radiation and convection losses within the furnace.

3. A furnace for the successive heat treatment of articles of manufacture comprising a central firing chamber and a substantially L-shaped extension through which the ware is carried at each end of said firing chamber providing separated terminal portions for the furnace and wherebyradiation from the firing chamber toward the inlet and outlet is subjected to multiple reflections and substantially retained within the furnace.

4. V furnace for successive heat treatments of articles of manufacture comprising an L-shaped preheating section forming a charging terminal for the furnace, a firing chamber connected at one end to the inner leg of said L-shaped section, and an L-shaped cooling section in which the inner leg of the L is connected to the opposite end of the firing chamber and forming a discharging terminal located at the opposite end of the furnace structure and spaced from the charging terminal.

5. A furnace for the continuous heat treatment of. articles of manufacture comprising a central firing chamber, two L-shaped extensions spaced apart from each other and continuous with said firing chamber, one of which is at one end of the firing chamber for preheating the articles and the other of which is at the other end of the firing chamber for gradually cooling the articles after the firing, and means for carrying ware through the chamber and its said extensions.

6. A furnace for the heat treatment of articles of'manufacture comprising a central firing section, an L-shaped preheating section connected with one end of said firing,

section, an L-shaped cooling section connected to the opposite end of said firing section, a slot in the roof of tinuous conveyer above said furnace, means connected to the conveyer and extending through said slot for transporting the articles under heat treatment, and shields carried by said means to reduce the radiation and convection losses from said furnace.

7. A furnace for the successive heat treatment of articles of manufacture comprising a central firing chamber and extensions at each end of said firing chamber continuous therewith but having portions at each end thereof each of said sections, a con-;

which are continuations of the furnace and through which the ware passes, said extensions being: bent away from the general direction of the central whereby thearticles are carried in a devious path'throughthefurnace and the radiation losses from the furnace are reduced, said extensions providing separated' terminals at opposite ends of the firing chamber.

8.- An open end furnace in which both ends are turned at an angle to the main body of the furnace, whereby radiationfrom the cen .tral' combustion chamber toward the ends is subjected to multiple-reflections and hence the; temperature of the central combustion chamber is substantially maintained at the value it would have if theends of thefurnace were in align-ment with the central combus-' tion; chamber and enclosed, and a continuous conveyer for transporting articles to be heated through the furnace, said conveyer being arranged to carry the ware through the turned ends of the furnace as well as through the main body thereof, the turned end portions providing separated charging and dischargingterminals. p

9. In combination with open end furnaces, a continuous conveyer forvtransporting articles to be treated throughthe furnace, a plurality of'travelingshields carried on the conveyer along with the articles through one end portion, thence through the combustion portion ,of theffurnace chamber and finally through the other end V portion,fthe radiation from the bustion chamber towards the ends being refiected away from the ends of the furnace by the shields, whereby the temperature of ,the combustion chamber is maintained at substantially enclosed. v i v 1 10,, In open end furnaces,a continuousconveyer for vtransporting articles to be treated through the'furnace, a plurality of traveling, shields on the conveyer which are carried along with the articlesthrough one end portion thence through the combustionfchamber comprising'the central portion of the furnace and finally] through the other end portion, the ends of the furnace being offset with respect to the central portion of the furnace, the shields and offset ends cooperating the value it wouldhave if' kept central cointo reducethe radiation from the central combustion chamber toward theends and to reflect such radiation away from the ends whereby the temperature a of the 'COlHbllSlllOIl chamber is maintained at substantially the value it would haveif enclosed.

ll. Thefurnace in claim 10 in whichpermanent and adj'ustable end doors are used whereby the shields are of substantially the same size as the endopenings through which they pass.

12. The method of a furnace for firing tinuously moving reducing heat losses in ware and wherein a conconveyor 1s employed which comprises placing; at the time ofload=' ing withware removable screens on the conveyer" carrying ware therethrough, said screens being so selected as to decrease heat transfer lengthwise of the furnace. I

13'. A continuous furnace having an endless conveyer thereover for transporting successive articles to be heat treated through the furnace, shields travelling with the ware and arranged transversely to the direction of travel of the ware for retarding the transmission of radiantheatlengthwise of the furnace, and adjustable shields at each end of the furnace which maybe adjusted to complement the shields which travel with the ware, whereby substantially the entire cross sectional area 7 of the furnace is blocked against loss of heat by radiation lengthwise of'the furnace.

14. A furnace for the heat treatment of articles of manufacture comprising a central firing chamber having extensions at each endv thereof forming separated terminal portions which are continuous therewith but offset with respect thereto, said extensions forming continuations of the furnace, a continuous conveyer for carrying articles through the furnace, including the extensions, and transverse shields on the conveyer for retarding the transmission of heat'by radiation in the direction of travel of theconveyer.

15. The method of operating a continuous furnace for the burning of ware wherein the ware is carried on supporting elements hung from a continuous conveyer which comprises attaching shields to the conveyerat intervals according to the character of the ware being enameled. i

16. A tunnel kiln designed for continuous operation over prolonged periods in which the ware is transported by means of an overiead conveyer which carries the Ware by means of hangers which project through a slotted roof in the furnace, said tunnel having its ends turned at right angles to the firing chamber and the conveyer track being similarly deflected so that ware can be carried through the furnace without the usual interruption of its progress at the inlet and outlet respectively. v

17. A tunnel 'kiln designed for continuous operation over prolonged periods having a slotted roof and overhead conveyer, means extending from said 'conveyer through said slot for vsupporting ware under treatment, and light adjustable shields carried by said supporting means and shaped to substantially prevent loss by radiation through the inlet and through the outlet of the tunnel.

In testimony whereof I have hereunto set my hand.

BOYD M. JOHNSON. 

